1. Field of the Invention
This invention is directed to a coating composition, in particular, to a coating composition having excellent corrosion resistance and good adhesion to aluminum or aluminum alloy substrates.
2. Description of the Prior Art
Modified epoxy resins crosslinked with amino silanes that are used to form primer coatings on aluminum substrates with improved flexibility and resistance to Skydrol® hydraulic fluid are disclosed in Noren et al. U.S. Pat. No. 4,520,144 issued May 28, 1985. The improved flexibility of the primer coating is provided by the isocyanate containing polysiloxane prepolymer that is post reacted with a low molecular weight epoxy resin. This post reaction step is a relatively long time consuming step and does not provide the rapid ambient cure currently required in a typical modern automotive, truck, bus or OEM (original equipment manufacturing) fleet market operation.
There is a need for a rapid curing composition that has excellent adhesion to untreated aluminum or aluminum alloy substrates that provides a flexible finish and has the properties that meet current requirements of the transportation industry both in the OEM market and in the refinish aftermarket. The novel composition of this invention meets these requirements.